1. Field of the Invention
The present invention relates to an ultrasonic imaging device for visualizing an inside of a sample by an ultrasonic testing.
2. Description of the Related Art
Conventionally, a method of two-dimensionally, mechanically scanning with a single focus type ultrasonic probe has been used to check whether a defective (delamination and boyd) on a semiconductor or an integrated circuit is present or absent through ultrasonic waves. This testing method performs transmitting and receiving of ultrasonic waves with a single focus type ultrasonic probe with a focus on a testing object part in a structure which is a testing sample, and a gate processing of echo waves (ultrasonic waves) reflected by the testing object part to obtain intensity information and time information of the echo waves (ultrasonic waves) reflected by the testing object part.
The obtained information of the echo waves is mapped on a two-dimensional space to generate inspection image information, so that the presence or the absence of defective can be checked on the basis of the inspection image information.
JP 05-232092 A discloses as an object of the invention “to easily and accurately detect a defective in a sample” and as structure of the invention “a transducer 1 for transmitting a pulse into a sample M and receiving echoes is connected to a transceiver 2 for generating the pulse and amplifying the echoes and at a rear stage thereof a gate circuit 3 for retrieving an echo at a given interval from the echoes.
Further, the gate circuit 3 is connected to a positive comparator 4, a negative comparator 5, a positive peak holder 6, and a negative peak holder 7, and their outputs are inputted into a control unit 9”.
Still further, JP 05-232092 A discloses “in the positive comparator 4 and the negative comparator 5, an earlier timing when one of the echoes first exceed a predetermined reference value is input into a delay circuit 8 which closes the gate circuit 3 after an approximately one cycle”.
Recently, an ultrasonic testing method using an array type ultrasonic probe has been used also. The array type ultrasonic probe is a prove having a plurality of piezoelectric devices arranged in line. Transmission and reception of the ultrasonic waves with delay in driving the elements is made for the piezoelectric devices in accordance with the predetermined scanning positions can focus ultrasonic waves, transmitted to the testing object, on the testing object. This focuses the ultrasonic waves on a point for transmission and reception similarly to the array type ultrasonic probe by disposing a lens in normal line directions of the respective piezoelectric devices or an array of the piezoelectric devices is disposed on a curved surface.
JP 11-304769 A discloses as a problem of the invention “to provide an ultrasound test method capable of detecting defectives occurring at positions having different depths in the sample accurately through one time inspection, and as solving means of the invention” an ultrasonic prove 1 provided with an array vibrators 3 comprising a plurality of vibrating elements 3a are arranged on an acoustic lens 2 is arranged to face the sample body 10. A focus FA of the acoustic lens FA and a focus FB made by electrically converging the piezoelectric vibrator are set to have different depths to accord the focuses on respective testing planes in the sample. When it is determined that there is a defective, two focuses are equalized to a testing plane on which existence of the defective is determined for the defective testing again.
Because the array type ultrasonic probe can electronically scan a plurality of piezoelectric devices, so that the ultrasound test can be performed more rapidly than the mechanical scanning by the single focus type ultrasonic probe.
JP 2003-107059A discloses as a problem of the invention “to provide an ultrasonic imaging device and a measuring method thereof which are simplified in an oscillator structure and capable of using a burst wave signal, if necessary, in a range where no interference occurs by smoothly varying transmission waves from a pulse signal to a burst wave signal”. Further, JP 2003-107059A discloses as solving means of the invention “It is an ultrasonic imaging device driving a ultrasonic probe 14 with a transmission wave signal to generate ultrasonic waves 16 and irradiating a sample 18 with the ultrasonic waves, detecting and converting reflected waves returning from the sample with the ultrasonic prove into a received wave signal, displaying on a display device an image of a given testing part of the sample through image display processing on the basis of the received wave signal. Only a burst wave oscillator 12 is provided to output a burst wave signal as a means for outputting the transmission wave signal and the minimum number of waves of the burst wave signal outputted by the burst wave oscillator is equal to or smaller than 1. The number of the waves of the signal outputted by the burst wave oscillator is controlled by a controller 15.
JP 2003-107059A discloses at a paragraph 0017 as an object of the invention “to provides the ultrasonic imaging device capable of measurement at a high resolution and image generation by narrowing a frequency band to decrease attenuation affection in order that the burst wave signal can be used, if necessary, in the range where no interference occurs by smoothly varying the transmission waves from the pulse signal to the burst wave signal with a structure of a circuit part of the oscillator generating the transmission waves simplified”.
However, JP 2003-107059A does not disclose on selection of an optimal frequency for a measuring sample.
A frequency optimal for visualizing an inside of the sample depends on a material forming the sample. Accordingly, it should be done to set an optimal ultrasonic wave frequency depending on the material also in a case where any one is used between the single focus ultrasonic probe or an array type ultrasonic probe.
However, conventionally, a frequency of the measurable ultrasonic waves was fixed for each ultrasonic sensor (ultrasonic probe). Accordingly, to change the frequency of the ultrasonic waves, not few ultrasonic wave sensors (ultrasonic probes) should have to be changed. Further, in the conventional ultrasonic sensor (ultrasonic probes), it have not be able to perform measurements with frequency of the ultrasonic waves being successively changed and compare the ultrasonic wave image in quality.